The present invention relates to a maleimide-based and/or an unsaturated dicarboxylic acid anhydride-based copolymer excellent in heat resistance, transparency, mechanical strength and moldability, unlikely to thermal degradation, small in an extent of coloration and deterioration occurring in the process of molding, and superior in appearance after molding, a thermoplastic resin composition comprising said copolymer and a rubbery polymer, and processes for producing said copolymer and said thermoplastic resin composition.
Recently, in the fields of electric instruments and automobile industry, there has been a tendency of attaching importance to a design property, and materials used in these fields have been required to have a high mechanical performance, a light weight and an excellent appearance for such a tendency. In order to satisfy such a requirement, polycarbonate-based resins and polyphenylene ether-based resins, both of which belong to a material field called engineering plastics, has been used, and SMI resin, namely a copolymer of styrene and N-phenylmaleimide, has been developed and used. Although these resins are superior in heat resistance, they are inferior in moldability. Currently, the shape of resin articles is becoming more complicated to satisfy the desire for a design property and their wall thickness is becoming smaller to satisfy the desire for lessening the weight. Under such a condition, an easiness of handling at the time of molding has been paid an attention to as one of the material performances also from an aspect of improving the product yield and saving energy and resources. For such a viewpoint, a resin material superior in moldability and having a heat resistance comparable to that of engineering plastics has been required.
In order to improve a heat resistance of thermoplastic resins, a resin composition prepared by blending a rubber-reinforced resin with an xcex1- methylstyrene-based copolymer using xcex1-methylstyrene as a component for the copolymer is used. In this case, an inclusion of xcex1-methylstyrene as a component of a resin matrix contributes to a heat resistance. Accordingly, this material has a fault that no sufficient heat resistance can be realized when the content of xcex1-methylstyrene is low, while thermal degradation readily takes place in the process of molding when the content of xcex1-methylstyrene is high.
With the aim of overcoming the above-mentioned fault of xcex1-methylstyrene-based resins, a method of using heat resistant resins comprising a maleimide-based copolymer or an unsaturated dicarboxylic acid anhydride-based copolymer has been proposed in JP-A 61-16955, etc. Further, JP-A-3-205411 has proposed a technique of producing such a maleimide-based copolymer or unsaturated dicarboxylic acid anhydride-based copolymer by the method of continuous solution copolymerization which is said to be desirable from the viewpoint of making uniform a comonomer distribution in the copolymer.
However, the above-mentioned maleimide-based copolymer and unsaturated dicarboxylic acid anhydride-based copolymer contain unreacted unsaturated dicarboxylic acid anhydride-based monomer or unreacted maleimide-based monomer etc., and these unreacted monomers are quite difficult to remove.
In case the unreacted monomers such as unsaturated dicarboxylic acid anhydride-based monomer, maleimide-based monomer or the like remain in the resin in a large quantity, there arises a problem that the resin becomes colored at the time of molding. Further, there is a problem that the unreacted monomers vaporize and exhale to form a silver streak on a surface of molded article to deteriorate an appearance of molded article. Further, there is a problem that the vaporized components of the unreacted monomers are deposited on a mold and contaminates the molded article as a soil to deteriorate an appearance of molded article. Although an operation of beforehand removing of volatile components such as water are generally conducted by subjecting a resin to a preliminary drying prior to molding, it is quite difficult to remove the unreacted monomers by such an operation.
Accordingly, a lowness of the content of unreacted monomers in a resin is very important to the molding work.
It is an object of the present invention to obtain a maleimide-based and/or unsaturated dicarboxylic acid anhydride-based copolymer which is low in the content of unreacted monomer such as a maleimide-based monomer, unsaturated dicarboxylic acid anhydride-based monomer and the like, superior in heat resistance, transparency, mechanical strength and moldability, unlikely to thermal degradation, small in an extent of coloration and deterioration occurring in the process of molding, and excellent in appearance after molding; and a thermoplastic resin composition comprising said copolymer.
The essentiality of the present invention consists in:
(1) a copolymer comprising a maleimide-based monomer unit and/or an unsaturated dicarboxylic acid anhydride-based monomer unit as constitutional components, wherein said copolymer contains an unreacted maleimide-based monomer and/or an unreacted unsaturated dicarboxylic acid anhydride-based monomer in an amount of 200 ppm or less and an adduct of a compound other than the constitutional components of said copolymer and said maleimide-based monomer and/or said unsaturated dicarboxylic acid anhydride-based monomer in an amount of 0.1 to 3,000 ppm;
(2) a thermoplastic resin composition comprising, as constitutional components, (A) 20-90 parts by weight of a maleimide-based copolymer comprising (a) 15-65% by weight of a maleimide-based monomer unit and (b) 85-35% by weight of at least one monomer unit selected from the group consisting of an aromatic vinyl-based monomer and other vinyl-based monomer (the total amount of the monomer units (a) and (b) is 100% by weight), (B) 80-10 parts by weight of a graft polymer obtained by polymerizing at least one monomer selected from the group consisting of an aromatic vinyl-based monomer and other vinyl-based monomer in the presence of a rubbery polymer, and (C) 0-100 parts by weight of other thermoplastic resin, wherein said thermoploastic resin composition contains unreacted maleimide-based monomer in an amount of 10 ppm or less, a volatile component other than said maleimide-based monomer in an amount of 0.5% by weight or less as a total volatile amount, and an adduct of a compound other than the constitutional components of said maleimide-based copolymer and said maleimide-based monomer in an amount of 0.1 to 3,000 ppm;
(3) a process for producing a copolymer comprising, as constitutional components, a maleimide-based monomer unit and/or an unsaturated dicarboxylic acid anhydride-based monomer unit which comprises adding a compound other than the constitutional components of said copolymer before, during or after polymerizing a monomer mixture comprising the maleimide-based monomer and/or the unsaturated dicarboxylic acid anhydride-based monomer, or to a copolymer comprising said monomer units as constitutional components obtained by the polymerization; and
(4) a process for producing a thermoplastic resin composition which comprises polymerizing a monomer mixture comprising a maleimide-based monomer, an aromatic vinyl-based monomer and/or other vinyl-based monomer to form a maleimide-based copolymer comprising these monomer units as constitutional components, and then adding to the resulting maleimide-based copolymer a compound other than the constitutional components of said maleimide-based copolymer, said graft copolymer, and optionally other thermoplastic resin.
As the maleimide-based monomer which can be used for the production of the maleimide-based copolymer of the present invention, maleimide, N-methylmaleimide, N-ethylmaleimide, N-(n-propyl)-maleimide, N-isopropylmaleimide, N-t-butylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-toluylmaleimide, N-xylylmaleimide, N-naphthylmaleimide and the like can be referred to.
Among these maleimide-based monomers, preferable are N-cyclohexylmaleimide and N-phenylmaleimide, and particularly preferable is N-phenylmaleimide. These maleimide-based monomers can be used alone or in combination of two or more.
As the unsaturated dicarboxylic acid anhydride-based monomers which can be used for producing the unsaturated dicarboxylic acid anhydride-based copolymer of the present invention, maleic anhydride, itaconic anhydride, citraconic anhydride and the like can be referred to, among which maleic anhydride is preferable.
The content of the maleimide-based monomer unit in the maleimide-based copolymer of the present invention is preferably in the range of 15-65% by weight, and more preferably in the range of 20-50% by weight. When the content of the maleimide-based monomer unit is less than 15% by weight, heat resistance of the composition which is an object of the present invention tends to become low. When the content of the maleimide-based monomer unit exceeds 65% by weight, there is a tendency that a fluidity of the composition is inferior and no molded product can be obtained at the time of molding or the resin formed is so brittle that the molded article can be cracked at the time of demolding from the mold.
In the unsaturated dicarboxylic acid anhydride-based copolymer of the present invention, the content of the unsaturated dicarboxylic acid anhydride-based monomer unit is preferably in the range of 5-50% by weight, and more preferably in the range of 10-40% by weight. When the content of the unsaturated dicarboxylic acid anhydride-based monomer unit is less than 5% by weight, the heat resistance which is an object of the present invention tends to become low. When the content of the unsaturated dicarboxylic acid anhydride-based monomer unit exceeds 50% by weight, there is a tendency that a fluidity of the composition is inferior and no molded product can be obtained at the time of molding or the resin formed is so brittle that the molded article can be cracked at the time of demolding from the mold.
The aromatic vinyl-based monomer which can be used in the present invention include, for example, styrene, xcex1-methylstyrene, vinyltoluenes such as p-methylstyrene and the like, halogenated styrenes such as p-chlorostyrene and the like, p-t-butylstyrene, dimethylstyrene, vinylnaphthalenes and the like, among which preferable are styrene and xcex1-methylstyrene. These aromatic vinyl-based monomers can be used alone or in combination of two or more.
As said polymerizable other vinyl-based monomers which can be used in the present invention, vinyl cyanide-based monomer, unsaturated carboxylic ester-based monomer and vinylcarboxylic acid-based monomer etc. can be referred to. As said vinyl cyanide-based monomer, acrylonitrile, methacrylonitrile, vinylidene cyanide and the like can be used, among which acrylonitrile is suitable for use as a starting material of heat-resistant ABS resin. As said unsaturated carboxylic ester-based monomer, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, phenyl methacrylate, isobornyl methacrylate, benzyl methacrylate, trichloroethyl methacrylate, cyclohexyl methacrylate and the like can be referred to, among which methyl methacrylate is preferable. These unsaturated carboxylic ester-based monomers can be used alone or in combination of two or more. As said vinylcarboxylic acid-based monomer, acrylic acid, methacrylic acid and the like can be referred to, among which methacrylic acid is preferable. These other vinyl-based monomers can be used alone or in combination of two or more.
In the maleimide-based copolymer of the present invention, the total content of the aromatic vinyl-based monomer unit and the copolymerizable other vinyl-based monomer unit is preferably in the range of 85-35% by weight, and more preferably in the range of 80-50% by weight. In the unsaturated dicarboxylic acid anhydride-based copolymer of the present invention, the total content of the above-mentioned monomer units is preferably in the range of 95-50% by weight, and more preferably 90-60% by weight.
In the maleimide-based copolymer of the present invention, the content of an unreacted maleimide-based monomer is preferably 200 ppm or less, more preferably 50 ppm or less and particularly preferably 30 ppm or less; and the content of total volatile components other than the maleimide-based monomer is preferably 0.5% by weight or less and more preferably 0.3% by weight or less. The content of an adduct of a compound other than said constitutional components of the copolymer and said maleimide-based monomer is preferably 0.1-3,000 ppm, and more preferably 0.1-1,000 ppm.
In the unsaturated dicarboxylic acid anhydride-based copolymer of the present invention, the content of an unreacted unsaturated dicarboxylic acid anhydride-based monomer is preferably 200 ppm or less and more preferably 150 ppm or less; the content of total volatile components other than the unsaturated dicarboxylic acid anhydride-based monomer is preferably 0.5% by weight or less; and the content of an adduct of a compound other than the constitutional components of the copolymer and said unsaturated dicarboxylic acid anhydride-based monomer is preferably 0.1-3,000 ppm.
If the content of the unreacted maleimide-based monomer exceeds 50 ppm or if the content of the unreacted unsaturated dicarboxylic acid anhydride-based monomer exceeds 200 ppm, the copolymer tends to become colored and inferior in transparency, and at the time of fabrication there can occur various troubles such as thermal coloration, bleed-out, flying of mists of maleimide-based monomer or unreacted unsaturated dicarboxylic acid anhydride-based monomer. As the total volatile components other than maleimide-based monomer and/or unsaturated dicarboxylic acid anhydride-based monomer in the copolymer, the monomers of the constitutional components, organic solvents and residues of optionally used polymerization initiator and chain transfer agent can be referred to. If total amount of these volatile components exceeds 0.5% by weight, heat resistance of the copolymer tends to be deteriorated and a silver streak can be formed at the time of molding. If the content of the adduct of maleimide-based monomer and/or unsaturated dicarboxylic acid anhydride-based monomer and compounds other than the constitutional components of said copolymer exceeds 3,000 ppm, heat resistance of the composition which is an object of the present invention tends to be deteriorated.
In the thermoplastic resin composition of the present invention comprising a maleimide-based copolymer, a graft polymer and other thermoplastic resin, the content of unreacted maleimide-based monomer is preferably 10 ppm or less and more preferably 5 ppm or less; the content of total volatile components other than maleimide-based monomer is preferably 0.5% by weight or less and more preferably 0.3% by weight or less; and the content of the adduct of a compound other than the constitutional components of maleimide-based copolymer and the maleimide-based monomer is preferably 0.1-3,000 ppm and more preferably 0.1-1,000 ppm; both based on the thermoplastic resin composition.
The thermoplastic resin composition of the present invention comprises a maleimide-based copolymer, a graft polymer and other thermoplastic resin preferably in amounts of 20-90 parts by weight, 80-10 parts by weight and 0-100 parts by weight, respectively, more preferably in amounts of 30-80 parts by weight, 70-20 parts by weight and 0-70 parts by weight, respectively, and particularly preferably in amounts of 30-80 parts by weight, 70-20 parts by weight and 3-70 parts by weight, respectively.
If the content of the unreacted maleimide-based monomer in the thermoplastic resin composition of the present invention exceeds 10 ppm, the thermoplastic resin composition tends to become colored and there can occur various troubles such as thermal coloration of the composition at the time of molding, bleed-out, and flying of mists of maleimide-based monomer. The total volatile components other than the maleimide-based monomer in said thermoplastic resin composition include volatile components originated from the maleimide-based copolymer, volatile components originated from the graft polymer and water etc. If total amount of these total volatile components other than the maleimide-based monomer exceeds 0.5% by weight, heat resistance of the thermoplastic resin composition tends to be deteriorated and silver streak can be formed at the time of molding. If the content of the adduct of the compounds other than the constitutional components of said maleimide-based copolymer and said maleimide-based monomer exceeds 3,000 ppm, heat resistance of the composition which is an object of the present invention tends to be deteriorated.
The maleimide-based copolymer used in the thermoplastic resin composition of the present invention can be the above-mentioned maleimide-based copolymer of the present invention.
The graft polymer used in the thermoplastic resin composition of the present invention can be obtained by polymerizing at least one monomer selected from the group consisting of aromatic vinyl-based monomers and other vinyl-based monomer in the presence of a rubbery polymer and thereby graft-polymerizing said aromatic vinyl-based monomer and/or said other vinyl-based monomer onto said rubbery polymer. As said aromatic vinyl-based monomer and said other vinyl-based monomer, the same aromatic vinyl-based monomers and copolymerizable other vinyl-based monomers as mentioned above as the constitutional components of the maleimide-based copolymer of the present invention can be referred to. The aromatic vinyl-based monomer and said other vinyl-based monomer used herein may be identical with or different from said constitutional components of the maleimide-based copolymer of the present invention, and acrylonitrile, styrene, butyl acrylate and the like are preferably used for this purpose.
As said rubbery polymer, the following can be used, though they are not limitative: rubbery polymer latices obtained by mixing a latex of a diene-based polymer such as butadiene-styrene copolymer obtained by polymerizing butadiene and/or styrene with an acid group-containing copolymer obtained by polymerizing methacrylic acid and/or n-butyl acrylate or the like; composite rubber latices of polybutadiene and butyl acrylate rubber obtained by adding butyl acrylate, allyl methacrylate and/or 1,3-butyleneglycol dimethacrylate or the like to the above-mentioned rubbery polymer latex and polymerizing the acrylate components and the like; polyorganosiloxane latices obtained by mixing an organosiloxane such as octamethylcyclotetrasiloxane or the like with xcex3- methacryloyloxypropyl-dimethoxymethylsilane or the like; composite rubber latices of an organosiloxane and a butyl acrylate rubber obtained by adding butyl acrylate, allyl methacrylate and/or 1,3-butyleneglycol dimethacrylate or the like to said organosiloxane latex and polymerizing the acrylate component and the like; etc.
As said xe2x80x9cother thermoplastic resinxe2x80x9d which can be contained in the thermoplastic resin composition of the present invention, vinyl-based polymers obtained by polymerizing a vinyl-based monomer such as acrylonitrile and/or styrene and the like can be referred to, though they are not limitative.
As a process for producing the maleimide-based and/or unsaturated dicarboxylic acid anhydride-based copolymer of the present invention, generally known polymerization processes can be adopted, and such a process can be carried out by adding a compound other than the constitutional components of the maleimide-based and/or unsaturated dicarboxylic acid anhydride-based copolymer before, during, or after the polymerization, or at any step of the production process such as drying, devolatilization, shaping, pelletizing, incorporation of other resins, stabilizers, etc. after the polymerization. It is preferable to add a compound other than constitutional components of the maleimide-based and/or unsaturated dicarboxylic acid anhydride-based copolymer after a completion of a solution polymerization in batch system or at the time of eliminating the volatile components by means of a devolatilizing extruder, and it is particularly preferable to add said compound at the time of eliminating the unreacted monomer, solvents, etc. by means of a devolatilizing extruder in a continuous solution polymerization system.
Similarly to the above, as a method for producing the thermoplastic resin composition of the present invention comprising a maleimide-based copolymer, a graft polymer and other thermoplastic resin, there can be referred to a method of adding a compound other than the constitutional components of the maleimide-based copolymer at the time of producing the maleimide-based copolymer, a method of adding a compound other than the constitutional components of maleimide-based copolymer before or during a melt-kneading of maleimide-based copolymer, graft polymer and other thermoplastic resin, etc.
The graft polymer contained in the thermoplastic resin composition of the present invention can be produced according to the generally known polymerization processes. In producing said graft polymer, 20-80 parts by weight of a rubbery polymer can be used as a solid component, together with 80-20 parts by weight of an aromatic vinyl-based monomer and/or other vinyl-based monomer.
The compound other than the constitutional components of the maleimide-based copolymer and/or the unsaturated dicarboxylic acid anhydride-based copolymer which is to be added to the composition is preferably a conjugated diene-based compound or a compound forming a conjugated diene-based compound through a reaction. As said conjugated diene-based compound, 1,3-butadiene, isoprene, chloroprene, cyclopentadiene, 1,3-cyclohexadiene, furan, anthracene and the like can be referred to. As said compound forming a conjugated diene-based compound through a reaction, dicyclopentadiene and the like can be referred to. Among the above-mentioned compounds, dicyclopentadiene is particularly preferable. These compounds are incorporated into the maleimide-based and/or unsaturated dicarboxylic acid anhydride-based copolymer of the present invention in the form of an adduct with a maleimide-based monomer and/or an unsaturated dicarboxylic acid anhydride-based monomer preferably in an amount of 0.1-3,000 ppm and more preferably in an amount of 0.1-1,000 ppm.
According to the need, a polymerization initiator, a chain transfer agent, a heat stabilizer and the like can be added at the time of producing the copolymer of the present invention. As the polymerization initiators which can be used in the production of the copolymer of the present invention, generally known organic peroxides and azo compounds can be referred to. Said organic peroxides include ketone peroxides, peroxy-ketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxy-esters, peroxy-dicarbonates and the like. As the chain transfer agents which may be used according to the need at the time of producing the copolymer of the present invention, mercaptans, terpene oils, xcex1-methylstyrene dimer and the like can be referred to. As the additives such as heat stabilizer which can be used according to the need at the time of producing the copolymer of the present invention, generally known ones can be used, although those obstructing the polymerization or making troubles such as coloration are undesirable.
In the production of the thermoplastic resin composition of the present invention, a dye, a pigment, a stabilizer, a reinforcing material, a filler, a flame retardant, a lubricant, an antistatic agent, a delustering agent and the like can be added according to the need.